Clarification of the neccessary autoloading of plugins...

...in the error message

Added links to the relevant documentation
I understand that, and am in favor of what you're trying to do here.

However, the thing is that before there was a short sentance that had been copied and pasted in 5 places but now there's a long sentence and 2 links in 5 places. Any change to the content requires changing it in 5 different places. It could have been changed before, but it hasn't - and now it's more obvious that it can be changed.

It might be better to conditionally output the composer warning in the layout rather than the individual messages. ala:

    if ($isAMissingClass) {
        echo $this->element('composer_warning');
    }